My last car had a 10 speaker factory "monsoon" sound system (front components, rear two-ways, and two 6'5" chassis mounted subs). Like the bose system (which, by the way, does not have dedicated subs to the best of my knowlege) the sound was only so-so. But I was able to "fix" the sound by using a new alpine head unit with a built in low pass/high pass crossover to send only frequencies over 80Hz to the monsoon speakers and the frequencies under 80Hz to an amplified sub. Without having to process the very low bass the monsoon speakers sounded awesome (WAY clearer) and could now handle a lot more power.

I think we could do the same thing with the bose speaker system...but using a slightly different method to keep the stock head unit. We could use a 5-channel amp with speaker-level inputs and a built in high pass/low pass cross over, hooking up a sub to the low pass amp output and the bose speakers to the highpass amp outputs (as long as the resistance matches). You could add your own large or small sub depending on desired bass and without having to handle low bass (only the mid bass) the bose speakers might just shine like my monsoon ones did.

Kicker makes a good unit for $580 (link below), and it even comes with a dash mounted level control for the subwoofer output. I'm gonna install it once my car gets in...
http://www.crutchfield.com/cgi-bin/S...=0&cc=01&avf=N


ps-I know $580 could go to new speakers but even if you did get new speakers you would want a nice amp so you could just attach them to this amp if the bose speakers didn't sound better...